Simulink Control Design™ - MathWorks

• Excitation of non-linearities


• Running into instabilities

Step 3: Estimating Frequency Response Using Chirp Input Signal

Another input signal you can use when estimating frequency response data from a

Simulink model is frequency chirp. Frequency chirp differs from sinestream in that the

frequency is instantaneously varied.

You can use chirp input signals to obtain quicker frequency response estimation.

However, the frequency estimation results obtained with chirp input could be less reliable

than the ones obtained with sinestream input because each frequency is not simulated

long enough to drive the system to steady state at that frequency. Create a chirp signal

that sweeps between the frequencies 0.1 and 10 rad/s logarithmically:

in_chirp = frest.Chirp('FreqRange',[0.1 10],'Amplitude',1e-3,...

'SweepMethod','logarithmic','NumSamples',3000);

Using the chirp signal, perform the frequency response estimation:

sys_chirp = frestimate(mdl,io,in_chirp);

Plot the results obtained with sinestream and chirp input signals together:

bode(sys,sys_chirp,'r')

5 Frequency Response Estimation